1. Field of the Invention
This invention relates to an ejector dwell control arrangement for a sorting apparatus.
2. Description of the Prior Art
It has long been desired to provide an electric sorting apparatus adapted to sort a variety of comestible or noncomestible articles without the necessity of changing or modifying the backgrounds against which the articles are detected and classified. To date, it is believed that a sorting apparatus able to sort a variety of articles without the necessity of changing the background for each article has eluded the art.
To understand the desirability of a sorting apparatus having a universally applicable background a brief overview into the state of the sorting art may be warranted.
Article sorting apparatus has traditionally utilized a background member disposed oppositely across an article stream from an optical viewer arrangement including an optical frame, an optical filter and a photoelectric detector. The frame defines a field of view or a viewing zone through which each article in a substantially singulated article stream passes. The intensity of light reflected from the article within the viewing zone at a predetermined wavelength compatible with the filter generates an electric signal output from the photodetector which is utilized in generating an article classification signal. The classification signal is utilized to classify the article viewed within the viewing zone on the basis of the presence of a predetermined physical characteristic therein, usually its color reflectivity.
In such arrangements, the background member is usually provided with the same color and reflectivity characteristics as an acceptable article. Thus, with no article within the viewing zone defined by the optical frame, an optical bias is imposed on the photocell due to the reflection of light energy from the background onto the cell. Accordingly, with no article in the viewing zone, an electrical signal output from the photocell corresponding to the output signal generated by an acceptable article is present.
When acceptable articles pass through the viewing zone no change in the electrical signal output occurs since the photodetector still is presented with reflected light at a wavelength adapted to generate an electrical classification signal output representative of an acceptable article. However, in a sorting arrangement, when an article having a portion thereon which is either darker or lighter than the color of an acceptable article enters the viewing zone, a deviation from the electrical signal output of the photodetector occurs. Typical prior art sorting apparatus have utilized such signal deviations to generate article reject signals. A reject signal known as a "light trip" occurs when the article within the viewing zone has a physical characteristic lighter than that of an acceptable article and thus generates a signal which deviates above the reference signal generated by the background. Alternatively, a reject signal known as a "dark trip" occurs when a portion of the article within the viewing zone includes a physical characteristic that is of a color darker than that of an acceptable article. The signal deviation corresponding to such a portion of the article appears as a decrease in the photodetector signal output.
In a monochromatic sorting apparatus, comparators are usually provided operable to generate article reject signals when the electrical signal output from the photodetectors deviates above or below predetermined cut points corresponding to light to dark trips, respectively. In a bichromatic sorting apparatus, the intensity of reflected light energy at two predetermined wavelengths is used to classify article reject signals representative of unacceptable articles.
It may be appreciated that the magnitude of the deviation from the background intensity signal is related to and dependent on both the reflectivity of the deflective portion of the article (either light or dark or unacceptably colored) as well as the percentage of the viewing area, or frame fill, which the defective article occupies. Also, as will be discussed herein, prior art sorting arrangements generate classification signals from the portion of the article which deviates from the defined norm, that is, from the spot on the article. The prior art then utilizes the occurrence of the reject signal as the time base to establish the initiation of the article ejector.
From the foregoing, the typical prior art sorting apparatus using a fixed background is believed disadvantageous in several respects. Since the background provides an output signal of the same intensity as an acceptable article, such an arrangement is not adapted to generate signals representative of the entry of an article into the viewing zone (i.e., article detect signals) or to provide signal representations of the length of the article within the viewing zone. The circuitry associated with the typical sorting apparatus is blind to an acceptable article. Accordingly, it is necessary to provide an independent article detector and article size arrangement for use with sorting apparatus of this type.
Further, each background member must be customized for the particular sorting task. A separate background member has to be provided for sorting tomatoes which differs in color reflectivity from the background member required for sorting peanuts. As a corollary, service maintainability problems are attendant upon typical prior art sorting apparatus. Once the appropriate background member is placed in position within the sorting apparatus, the presence of dust or other foreign matter, as well as the impingement of article juices or fading of the background member, necessitate fairly periodic background changes. Yet, to place the background in a sealed and unaccesible position to guard against these factors generates maintenance and upkeep problems.
Due to the fading and clouding of the background member for the reasons set forth immediately above and due to electrical amplifier drift, it is often necessary to provide some sort of normalizing or nulling arrangement adapted to obviate the effects to the background occasioned by the passage of an article stream through the viewing zone. For example, U.S. Pat. No. 3,899,415, issued to Hoover and Codding and assigned to the assignee of the present invention relates to a normalizing arrangement for sorting apparatus. U.S. Pat. No. 3,382,975, issued to M. C. Hoover and assigned to the assignee of the present invention relates to a normalization control apparatus which includes a circuit arrangement adapted to control signal nulling when no article is in the viewed area.
Experiences with the sorting apparatus of type having the background member of the same color as an acceptable article next led practitioners in the art to utilize a non-reflective background region in an attempt to eliminate the requirement for a background member. Typical of the sorting apparatus using a non-reflective background region is that described in U.S. Pat. No. 4,088,227, issued to James F. Lockett and co-pending application Ser. No. 704,651, filed July 12, 1976 in the names of John D. P. Jones, James F. Lockett, Elias Codding and Miles Smither, now U.S. Pat. No. 4,134,498, and copending application Ser. No. 704,697, filed July 12, 1976 in the name of James F. Lockett, now U.S. Pat. No. 4,241,835, all assigned to the assignee of the present invention. However, the use of the non-reflective region as an alternative for elimination of the background against which the article being sorted is viewed also presents several perceived disadvantages.
Of course, the most obvious disadvantage of using a non-reflective background as the basis for classification of the article is the inability of such a background to provide an article reject signal representative of a dark or black spot on the article. Such potential defects are masked when a non-reflective background is used as the basis of the comparison. Furthermore, both light trip and dark trip activities cannot be effectively performed until the article being viewed completely fills the entire viewing area defined by the frame. Until that time, as the photodetector output signal intensity curve moves from zero intensity (representative of the view of the non-reflective background) up to the full frame signal intensity deviations on those portions of the article which are in view before the entire frame is filled usually go undetected. Furthermore, each article generates a dark trip signal (that is, the photodetector output signal trace falls below the dark trip cut point) as the article passes from the full frame view. Accordingly, based on such an occurrence, every article being sorted would be eliminated as unacceptable.
To overcome these perceived difficulties, it is believed to be advantageous to provide signal information only when the article completely fills the frame. The most obvious expedient to achieve this end would be to define the viewing zone by using a frame of a scope such that most articles would, upon entry thereinto, completely fill the viewing zone. However, this is obviously impractical for some articles. For example, rice grains or coffee beans are inherently incapable, due to their physical size, of completely filling a viewing zone. The results of the search for a sorting apparatus having a uniformly acceptable background useful for sorting any article presents the conclusion that, instead of eliminating the background, one must provide two backgrounds, each of different reflectivities. By providing two backgrounds, for example, one reflective and one non-reflective, the advantages attendant upon each type background are complemented and the disadvantages overcome. However, provision of two backgrounds effectively doubles the problems of fading or splattering. Furthermore, two backgrounds would require changing each time the article being sorted varies.
It would be advantageous, it is believed, to provide a sorting apparatus having an arrangement adaptable to produce the optical equivalent of two "background" members without physically defining a traditional background member.
It would be advantageous to provide a sorting apparatus wherein a signal representative of full viewing zone output may be generated without the frame being filled in actuality. That is to say, it is believed to be of advantage to provide a signal output equivalent to a full frame output regardless of the percentage of the viewing zone actually being occupied by an article. It is recalled that it is only when a full frame output is present that signal deviations above and below the acceptable norm (that is, light trip or dark trip) are generated representative of article unacceptability.
It is believed to be of advantage to generate and utilize an electrical output signal representative of the percentage of frame fill of an article and use that percentage frame fill signal to scale the signal intensities derived by photodetectors viewing one or the other of optically imposed backgrounds.
It is believed to be advantageous to provide a sorting apparatus characterized by a viewing arrangement adapted to optically define two "backgrounds" and having associated electronic circuitry operating in a digital mode to provide two electrical signals, each representative of the reflectivity characteristic of the same area of an article within a field of view defined by an optical frame. Each of the signal outputs is generated by a suitable electrical signal generator, as a photocell, in response to reflected light energy detected against a different one of the optically defined reflectivity "backgrounds", one "background" having a higher reflectivity level than the other. Typically, "backgrounds" representative of 0% reflectivity and 100% reflectivity may be utilized. It is also believed to be beneficial to utilize the signal outputs generated by the photodetectors against the divergent intensity "backgrounds" to generate an electrical signal representative of the percentage of the viewing zone, or "frame fill" occupied by the article. Yet further, it is believed to be advantageous to utilize the derived percentage of frame fill to scale the signal intensity generated from one or the other of the photodetectors associated with each "background" to provide an electrical signal representation of full frame percentage reflectivity of the article.
As is discussed above those prior art sorting apparatus which use a background member having the same reflectivity characteristic as that of an acceptable article are blind to the entry of the article into the viewing zone. It is important for various reasons to ascertain the entry and exit times of an article into and out of the viewing zone as well as to provide an indication of article length. Accordingly, prior art sorting apparatus usually utilize some photodetector arrangement responsive to an interruption or diminution in the intensity of the light beam incident thereon as an indication of the detection of a product.
Therefore, it is believed advantageous to utilize the same electrical signal representation of the percentage frame fill to both scale the signal intensities derived by the photodetectors to generate reflectivity percentages and to provide an indication of the entry and exit of an article into and from the viewing zone. It would be of advantage to provide an electrical article detect signal representative of the presence of an article within the viewing zone when the percentage frame fill exceeds a predetermined threshold percentage frame fill. Further, it is believed advantageous to provide a sorting arrangement wherein the threshold percentage frame fill required before an article detect signal is generated may be adjustably controlled.
As noted, the percentage reflectivity of an article can be utilized to classify that article as acceptable or unacceptable if the reflectivity figure is above or below predetermined reference cut points. This is alluded to earlier as a "light" or "dark" trip. This technique is usually utilized when sorting articles and rejecting them on the basis of blemishes or defects on their surface.
It is also possible and a usual prior art practice to sort articles based on the reflected intensities of light energy at two predetermined wavelengths. Such bichromatic sorts rely upon some ratio or other functional relationship between the reflected light intensities at each of two predetermined color wavelengths to classify articles as acceptable or unacceptable. It is also known in connection with bichromatic sorting apparatus to utilize the reflected intensities at the predetermined color wavelengths to generate a reject signal when the article within the viewing zone is a foreign object. For example, the co-pending application of James F. Lockett, Ser. No. 829,485, filed Aug. 31, 1977, and assigned to the assignee of the present invention relates to a foreign object discriminator arrangement.
It is known in the prior art to utilize the electrical signal intensities of light energy reflected from an article being sorted at each of two predetermined color wavelengths to locate a point in a Cartesian coordinate system, each coordinate corresponding to one of the reflected light intensities. For example, the electrical signal outputs of reflected light energy at each color wavelength may be used to illuminate a point on the face of a cathode ray oscilloscope. From repeated trials with a plurality of acceptable articles, it is then possible to identify the portion of the face of the oscilloscope that points corresponding to acceptable (or, alternatively, unacceptable) articles cluster. A masking sheet, usually cardboard material, is then fabricated by hand and disposed over the face of the oscilloscope. In this manner, a photoelectric detector placed in proximity to the face of the oscilloscope is then shadowed so that only the illuminated points in the exposed portion of the face of oscilloscope are responded to by the photodetector. As may be appreciated, this time-consumming and tedious process must be used to generate a mask for each article type sorted.
In view of the foregoing, it is believed to be advantageous to provide a sorting apparatus having an electronic classification arrangement responsive to the signal representations of the reflected light intensities at each predetermined color wavelengths to address a programmable memory arrangement. The memory arrangement includes a plurality of memory storage locations, each one of which is addressable by a unique combination of reflected light intensities at each of the predetermined color wavelengths. Thus, within the storage locations of the memory arrangement, a "profile" region of acceptable or unacceptable articles may be defined. It is believed advantageous to provide such a programmable classification arrangement such that various acceptable/unacceptable profiles for each of a plurality of articles may be quickly and efficiently loaded into the appropriate memory locations.
Once an article has been classified (either monochromatically, bichromatically, or otherwise) as unacceptable it must be eliminated from the article stream through the operation of an article ejector element. The article ejector element may conveniently take the form of a mechanical element extendable into the path of the article stream to deflect the rejected article therefrom. It is also common to utilize ejector elements of the type operative to remove rejected articles from the article stream by directing a jet of pressurized fluid (either a liquid or a gas) to deflect the article from the article stream.
Such ejectors are typically driven under the control of an ejector control arrangement which receive an article reject signal after that signal is delayed for a predetermined period of time sufficient to permit the article to traverse the distance from the viewing zone to the ejection zone. Since it is possible for a plurality of articles to pass through the viewing zone and be appropriately classified before the first of those articles traverses the distance from the viewing to the ejection zone, it is typically necessary to provide some sort of storage arrangement wherein signal representation of the acceptability or unacceptability of each of the articles is stored for the predetermined delay time. At the expiration of that delay period the classification signal, termed an article reject signal if the article has been classified as unacceptable, is withdrawn from the storage or delay arrangement and applied through suitable circuitry to generate an article eject signal to the ejector driver. The driver responds to the article eject signal to initiate ejector operation to deflect the rejected article from the article stream.
It is noted above that the classification signal which serves as the basis for the article reject and article eject signals is typically generated when the defective portion of the article enters into the viewing zone. Thus, due to the fixed nature of the predetermined time delay of the system, ejector operation is initiated when the same defective portion of the article which generated the unacceptable classification enters into the ejection zone. Such an arrangement is not disadvantageous if the defective portion of the article happens to fall toward the mid-portion of the article. However, if the defective portion of the article happens to occur toward the trailing edge thereof, ejector operation is not initiated until that same trailing portion of the article enters the ejection zone. This may prove to be disadvantageous in some situations. Holding ejector operation until the entry of the defective portion of the article into the ejection zone may result in the great majority of the ejecting force produced thereby being directed toward the next-successive article in the article stream with only a small, and perhaps ineffective, portion of the ejecting force being directed against the article carrying the defect.
Accordingly, it is believed advantageous to provide an ejector control arrangement operative to initiate ejector operation to apply an ejecting force (either of the mechanical or pressurized fluid type) against the same predetermined portion of each article entering the ejection zone regardless of the location on the article of the defective portion causing the unacceptable classification thereof. It is believed advantageous to direct the ejecting force toward the article having the defect thereon rather than toward the defect itself. Such an arrangement is believed advantageous in that it increases the accuracy with which the ejecting force is applied and thereby increases the efficiency and reliability of the sort.
It is also believed of advantage to provide an ejector control arrangement which utilizes storage elements operative to store only article reject signals. Since the great majority of the articles being sorted are classifiable as acceptable, memory storage capability may be reduced at a concomitant reduction in cost if only article reject signal information generated by an unacceptable article is stored and utilized to generate an article eject signal. Furthermore, it is believed advantageous to use as memory storage and delay elements registers of the type which output data stored therein on a first in-first out basis. This eliminates the need for electrical signals to increment data through various memory stages.